You can download appropriate drivers for the lan directly if you know the manufacturer of the lan chip i.e intel etc,or it will be on mobo's manufacturers site hopefully

the usb drivers may or may not be separate drivers or they may be part of the mobo chipset drivers

getting them back to a working state i assume you have a functional dvd drive preferably using a rw disc so burning them to a rewritable disc is a go or place the necessary drivers on the hdd directly by utilizing an external housing & install from there

The drivers themselves may still be in the system32 folder unfortunatley knowing which ones are which is anyone's guess unless the option to delete was used by mistake

you may want to look at drivermax or some other similar free software even if only used to create an initial driver backup,however a better option is using imaging software like easeus todo backup (free version of coarse)actually make that imaging comment mandatory,it makes system no restore look like a pansie

should be in legacy mode but is not a default & not for usb as is not legacy. do want usb keybd\mouse enabled in bios for dos so will work in safemode. want to find out if the mouse will work in safemode or not.